Welding has evolved in mechanical engineering to a production process with broad applications which is adopted in particular in the case of light construction. Welding also affords an excellent opportunity to reduce the assembly cost of components. In the production of motor vehicles, in particular, welding is the main process for body assembly. Workpieces which serve as fastening and/or holding elements are welded on the body.
It is known to arrange, for example, solid bolts on the body by welding. The welding process as such is substantially automated. The positioning of the workpieces, in particular in the vehicle body region, also takes place substantially automatically. Apparatuses which combine a welding device and a supply device for workpieces are also known.
For the tack welding of workpieces, in particular strip-form workpieces, welding guns are provided with tack grippers. These tack grippers are designed in the manner of tongs. As a result, these tack grippers have a plurality of mechanically moving parts. Welding spatter which impairs the operability of the mechanically moving parts of the tack gripper can be formed during the welding process. In addition to such welding spatter, the mechanically moving parts are contaminated so the mechanically moving parts are subject to increased wear in the course of time. It may also happen that the holding force of the tack gripper no longer suffices as the tong-form tack gripper is inaccessible. It has also been found that contamination on the surfaces of the tack gripper adversely affect the reliable supply of current owing to welding spatter and that the desired resultant weld is not therefore always obtained. As a result, the welds have to be reworked under certain circumstances.